This invention relates to a method of operating an automated land maintenance vehicle, particularly, although not exclusively, a vehicle in the form of a mower.
The aesthetic appearance of turfed sports areas such as football pitches or golf courses is very important especially if the area is shown on television. Recently there has been a growing trend for ground maintenance staff to produce increasingly precise and intricate mowing patterns on the turfed surface.
Another and probably more important aspect of the job of ground maintenance staff is maintaining a good playing surface. Various factors may affect the quality of the playing surface, such as the sport being played (different sports damage different areas of the pitch), the local climate, the soil makeup and the frequency of use. There has been always been a requirement for ground maintenance staff to provide a high standard of playing surface for one of two reasons; maintaining a good playing surface against high usage of the football/rugby/American football/baseball and golf areas and to compete for premier sporting events such as high profile golf tournaments.
Conventionally, intricate mowing patterns are put onto the surface by manually pushing or driving the mower around on the surface in order to both cut the grass and to mark the desired mowing pattern. The pattern is achieved by rolling the grass in a particular direction after it has been cut, so that when the area is viewed, the shades produced by mowing in different directions define the pattern. Mowing and/or rolling a standard pattern may take several hours, while more intricate ones will take even longer. This makes for a long and boring job for the ground maintenance staff.
When maintaining a playing surface, the ground maintenance staff generally aim to maintain the grass coverage over the whole surface. Certain factors are considered before ground maintenance staff carry out any mowing or rolling. The factors include: considering areas of high wear (football pitches are prone to high wear in the goal mouth and center spot areas), areas of water logging or dryness and areas of high maintenance wear (excessive turning of maintenance vehicles or trenching due to machines following the same path time after time). The maintenance staff will then decide which areas to mow or roll based on an assessment of the whole surface. Parts of the pitch that are subject to any of the factors indicated above may have to be avoided during a maintenance task. This will increase the time required for the task, as more turning will be needed to carry out an increased number of strokes necessary to avoid the areas that are left to rest and recover.
Robotic mowers operate within a predefined area, mowing the area in a random or predefined route. Domestic robotic mowers exist that mow in parallel lines and these cover the whole mown area with the same pattern. They cannot avoid specific areas of grass unless a physical object such as a bumping board or an energized wire bound the areas.
When these mowers produce patterns, they are always in straight lines. Conventionally, the operator of the mower does not have the option of selecting a circular pattern or areas where grass may be deposited. Indeed due to the limitations of their guidance systems and the size of the area they are designed to cut, it is not uncommon for these domestic machines to miss parts of the area, leaving uncut grass.
Further robotic systems exist whereby the robotic mower has a sensor and computational means for determining its position within an area. Such positional data can be used to navigate the robot in predetermined routes in order to cover the area to be mown. Positional data may be captured by a variety of means, the most common being triangulation or trilateration from fixed known reference positions. Such reference points can be geostationary satellites (GPS) or ground based references that may be sensed by the robot vehicle. Optical and radio based systems are the most common means of determining mobile robot positional data. This positional data may have increased accuracy when averaged with inertial navigation devices that may include odometers, compasses and accelerometers.